To be honest I have noticed occaisonally blood and nearly always rodent urine and feces left on the newspaper afterward. I also leave my snakes in privacy for several days after feeding (usually till some of the meal has passed through them). I know that those things aren't good to have in the enclosure but I always thought it being there for a few days till the snake is ok to be handled again wasn't a big deal, maybe I'm wrong though. Best arguement yet in favour of using feed boxes.
I feel a little light headed... maybe you should drive...